The present invention relates to a brake with two discs of fixed spacing.
Single-disc brakes have an inherent limitation in that the disc has only two friction surfaces.
It is known to overcome this limitation by multiplying the number of discs. However, in most cases, this type of multiple-disc brakes comprises a stack of alternate discs and friction rings integral in terms of rotation, but free in terms of translational motion relative to a rotating axle and relative to a stationary cylinder respectively.
In current practice, these complex and costly brakes are reserved for aeronautics.
Where mass-production motor vehicles are concerned, however, the aim is to manufacture brakes which are both simple and economical and which can be serviced and maintained at the least possible cost.
The basis for a solution involves producing a brake with two discs of fixed spacing, thus avoiding the problems inherent in the abovementioned brakes with sliding discs. In fact, the fixed mounting of two discs parallel to one another presents very few difficulties.
In contrast, the main problem is in the arrangement and control of the two pairs of friction elements and of the supporting members associated with them.
U.S. Pat. No. 4,505,363 provided a brake with two discs of fixed spacing comprising a stationary support common to two calipers and extending over an angular sector of approximately 180.degree.. The two calipers are composed of pieces in the form of risers engaged axially slidably in means for guiding the common stationary support circumferentially one after the other, head to foot, the hydraulic motors associated with the two calipers being located on either side of the pair of discs.
There are many disadvantages of such a brake: it has a large axial bulk. Moreover, to function, it requires a considerable space in order to allow for the removal of the calipers when the linings have reached their maximum acceptable wear. Finally, the yoke and the calipers cover the discs over more than half their surface, this being detrimental to their ventilation and their cooling.
The maintenance of such a brake also presents disadvantages: mounting all the movable elements of the brake slidably on transverse slideways raises other problems well known to an average person skilled in the art: corrosion of the sliding surfaces, jamming by wedging when skewing occurs, difficulty in removing the brake, if only to replace the pads carrying the friction linings.